PHNOM PENH, Jan 10 (Reuters) - Tens of thousands of garment workers have returned to work in Cambodia since a strike for higher pay was put down with deadly force by the authorities last week but employers are now piling up lawsuits against trade unions over the two-week dispute.

The garment makers' association said most workers had returned to work around the country by Friday although only about 60 percent had shown up at the Canadia Industrial Park in the capital, Phnom Penh, where military police opened fire on Jan. 3, killing three strikers according to the government.

The park is home to factories that make clothes for Western brands such as Adidas AG, H&M Hennes & Mauritz AB and Puma SE.

"The lawsuits will focus on incitement to strike, damage to property and assets, coercion and threatening workers who want to work," Ken Loo, secretary-general of the Garment Manufacturers Association in Cambodia (GMAC), told Reuters.

Khieu Sambo, an attorney representing firms against the six unions involved in the strike, told Reuters that more than 150 factories had filed lawsuits and more were being prepared.

Chea Mony, president of the Free Trade Union, one of those targeted, said the judiciary was politicised but he would still fight the charges in court.

"They sued us because they want to intimidate us so we won't strike any more and we won't help the workers," he said. "We are not afraid."

The U.N. human rights agency said this week five people were killed and 20 wounded by gunfire and beatings when military police opened fire on the workers, who were demanding a rise in minimum pay to $160 per month from $100.

The workers, allied with an anti-government protest movement, were among 350,000 who had gone on strike since Dec. 24, threatening to cripple the country's main export industry, which earns more than $5 billion in revenue a year.

The opposition Cambodia National Rescue Party (CNRP) had been protesting against what it called the fraudulent election victory in July won by long-serving Prime Minister Hun Sen. It wants the vote to be re-run.

The strike ended after the police crackdown, while the CNRP called off its protest the next day after the authorities dismantled its protest camp in a Phnom Penh park.

The CNRP had promised to double the minimum wage in the garment sector to $160 a month if it won power.

The government had offered first $95, then $100, a rise of 25 percent. The unions rejected that but GMAC's Ken Loo said a minimum wage of $100 would come into force on Feb. 1. (Reporting by Prak Chan Thul; Editing by Alan Raybould and Robert Birsel)